Electrical-to-mechanical converter and switch assembly

ABSTRACT

An electrical signal input device which is operated by a small AC or DC signal with mechanical movement being obtained as a result of the signal. A container having a puddle of mercury therein is supported so that in a first position the surface tension of the mercury causes the mercury to stand above an elongated portion of the container. A conductive fluid inside the container is in contact with the surface of the mercury. A starter electrode engaged with the conductive fluid when energized causes the surface tension of the mercury to be broken so that the mercury runs into the elongated portion of the container. The weight of the mercury causes the container to pivot and thereby close a main load switch.

United States Patent l72| Inventor Elwood G. Norris 2505 20th East, Seattle. Wash. 98102 |2ll Appl No. 850,9!2 [22] Filed Aug. I8. 1969 [4S] Patented July I3, I97] [54] ELECTRICAL-TO-M ECHANICAL CONVERTER AND SWITCH ASSEMBLY 7 Claims, 5 Drawing Figs.

(52] U.S.Cl 3371!", 200/152. 335/49, 337/! I8 [5|] Int. Cl ..ll0ll| 29/04, H0lh 37/36, HOlh 6H0] [50] I-leldolSearch 200161.5l, lSZ', 335/49, 54; 337/l, H4, 1 l5, H6. H8, I I9, 120, 306, 417

[56] References Cited UNITED STATES PATENTS 3,38l .248 4/l968 Furth ZOO/l 52 X 2.0l2,49l 8/1935 Agnew l.488,95l 4ll924 Stoelle t.

ABSTRACT: An electrical signal input device which is operated by a small AC or DC signal with mechanical movement being obtained as a result of the signal. A container having a puddle of mercury therein is supported so that in a first position the surface tension of the mercury causes the mercury to stand above an elongated portion of the container. A conductive fluid inside the container is in contact with the surface of the mercury. A starter electrode engaged with the conductive fluid when energized causes the surface tension of the mercury to be broken so that the mercury runs into the elongated portion of the container. The weight of the mercury causes the container to pivot and thereby close a main load switch.

POWER SUPPZ) LOAD PATENTEU Jun 3 m:

POWER 25 Pow R Jz SUPPLY H 7 l/YVE/YTOR. E 1 W00 (9 Maw/5 ATTOF/VE Y5 ELECTRICAL-TO-MECHANICAL CONVERTER AND SWITCH ASSEMBLY A need has long existed for low-cost and simple switch devices capable of responding to a small control signal for switching a heavy-load current. In many requirements it is desirable to obtain a mechanical movement in response to an electrical signal and thus various types or relay assemblies have been devised. Unfortunately the cost of such devices is relatively high, particularly when a relay of small physical dimensions is required. In addition it is found that most relays are current and voltage sensitive and in general are designed for either AC operation or DC operation but not both. A prime example of an art wherein it would be advantageous to have a simple and low-cost switch which provides a mechanical movement in response to a small electrical signal is in the record changer art.

Thus it is an object of the present invention to provide a simplified and low-cost electrical switch. Another object is to provide such a switch which produces mechanical movement in response to a small electric control signal. Another object is to provide such a switch assembly which responds to either alternating or direct current control signals. A further object of the present invention is to provide a low-cost electrical-to mechanical converter.

An additional object of the present invention is to provide an electrical switch which is suitable for tripping the changer mechanism of a phonograph record changer assembly with a small electric current serving to produce a mechanical signal.

The above and additional advantages of the invention are achieved through the use of a pivoted container having in one end thereof a depression filled with mercury and an elongated portion extending from the depression to a point on the opposite side of the pivot point of the container. The pool of mercury in the depression is of a volume such that due to the surface tension of the mercury a portion thereof stands above the level of the extended portion of the container. Thus when the surface tension of the mercury is broken the mercury flows into the extended portion to cause an unbalance of the container. As a result the container pivots with the mercury flow ing into the elongated portion. Thus a mechanical movement is obtained when the surface tension of the mercury is broken.

In order to provide a simple arrangement for breaking the surface tension of the mercury the container has a conductive fluid in contact with the surface of the mercury while it is standing in a pool in the depressed portion of the container. One electrode of a control circuit is engaged with the pool of mercury and a starter electrode is engaged with the conductive fluid. It is found that when a small current passes between the two electrodes, the conductive fluid by spreading the charge across the surface of the mercury causes the surface tension of the mercury to be broken so that the mercury flows into the elongated portion of the container. The resulting movement of the container can then be used for performing a desired mechanical function such as tripping the changer mechanism of a phonograph record changer or closing the contact of a main current-carrying switch assembly. A simple reset assembly is provided.

The above as well as additional advantages and objects of the invention will be more clearly understood from the following description when read with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of a preferred embodiment of the switch assembly in combination with the load circuit and triggering circuitry for the switch.

FIG. 2 is an end view partially in cross section showing the apparatus of FIG. I.

FIG. 3 is a perspective view of the switch assembly of FIG. 1.

FIG. 4 is a diagrammatic illustration of a further embodiment of the invention illustrating a reset mechanism for the switch assembly.

FIG. 5 is an illustration of a switch similar to that of FIG. 4 with the switch of FIG. 5 being in its activated position.

Turning now to the drawings there is illustrated a nonconductive container I0 which can for example be made of glass. The container I0 has a set of cylindrical depressions 10A and 108 provided in the sides thereof so that the support rods I! and I2 carried by the pivot supports I3 and I4 can support the container 10 for pivotal motion about the support rods 11 and 12. The left end of the container I0 is provided with a depressed portion 10C having a puddle of mercury l5 disposed therein. Extending to the right from the depressed portion 10C is an elongated portion of the container with the lower surface of the elongated portion being above the bottom of the depressed portion IOC but below the top surface 15A of the puddle of mercury. The remainder of the interior of the container 10 is filled with a conductive fluid 16 such as potassium hydroxide. The pivot points MA and 10B of the container 10 are located such that when the pool of mercury I5 is in the condition illustrated in FIG. 1 the elongated portion of the container "1D is approximately horizontal.

A starter electrode 20 connected by the switch 2| to the power supply 22 is located in the conductive fluid 16. A second electrode 23 disposed in the pool of mercury 15 is connected by lead 24 to the power supply 22.

A load circuit is illustrated as including the main-load power supply 25 connected to the electrical load 26 by means of the mechanical switch 37 which is positioned beneath the right end of the pivoted container 10.

The switch of FIGS. 1, 2 and 3 operates as follows. Prior to breaking the surface tension of the pool of mercury 15 the mercury stands in the left end of the container 10 so that the container 10 is in its most counterclockwise position and is engaged against the stop element 27. When a small current is passed from the electrode 20 through the conductive fluid 16 to the pool of mercury IS it is found that the surface tension of the pool of mercury is broken so that the mercury runs into the elongated portion 100 of the container 10. The weight of the mercury flowing into the right end of the container 10 causes the switch assembly to move clockwise so that the elongated portion 10D engages the second stop member 28. Thus it will be seen that the small electric signal gives rise to mechanical movement. As will be obvious to persons skilled in the art this mechanical movement can be used to accomplish various objectives. For example in FIG. 1 the switch 37 is closed in response to mechanical movement of the container 10 so that power supply 25 will provide current of any desired magnitude to the load 26. The mercury switch can be manually reset or a simple electrical reset circuit driven by the main-load current can be used.

While various types of switch assemblies can be actuated in response to the mechanical movement achieved from the pivoting of container 10, it will be seen in FIG. 3 that a simple switch assembly is provided by the conductive member 30 secured to the right end 10E of the container 10 with the conductive member 30 being positioned for engagement with the electrical contacts 3! and 32 located in alignment with and below the conductive member 30. Thus the battery 33 will selectively apply power to the load 34 in response to the small control signal applied between electrodes 20 and 23. A conventional mercury switch could also be secured to the new switch of this invention for controlling current flow. In such an arrangement a separate cavity for a separate volume of mercury would be activated by the movement obtained from the electric input signal.

In the embodiment illustrated in FIG. 4 a substantially spherical housing 40 has an upwardly extending elongated portion 40A, a downwardly extending elongated portion 408 and a rightwardly extending elongated portion 40C. The mercury 41 extends above the horizontal surface 40D of the rightward extension 40C when the surface tension of the mercury has not been broken. As in the previous embodiment, the remainder of the container is filled with a conductive fluid 42 such as potassium hydrolide. Starter electrode 43 is connected by lead 44, switch 45, resistor 46, and lead 47 to the power supply illustrated as the battery 48. Electrode 49 in the pool of mercury 41 is connected to the other terminal of the battery 43 by lead 50. The container 40 is pivoted at in a manner similar to the details illustrated in FIGS. l, 2 and 3.

The manner of operation of the embodiment illustrated in FIG. 4 is substantially the same as that previously described in that when a small current is applied between the conductive fluid 42 and the pool of mercury 41 the surface tension of the mercury is broken so that it flows along the surface 40D into the right end of the extension 40C. As a result the container 40 pivots clockwise and closes the switch 55 so that power is applied from the power supply 56 to the load 57. The load circuit 57 in the embodiment illustrated in FIGS. 4 and 5 in turn controls a reset device 58 having a reset plunger 59 disposed beneath the extension 40C of the container 40. The reset device 58 could be a conventional relay or another mercury switch of the type disclosed herein. Through the use of wellknown timing circuits the reset device 58 will be operated at a selected time by the load circuit 57 to cause the plunger 59 to move the container 40 counterclockwise to its original position. When the container 40 is returned to its counterclockwise position of FIG. 4 and the switch 45 is opened it is found that the mercury again assumes the condition illustrated in FIG. 4 with the surface tension of the mercury holding a portion of the mercury above the surface 400. FIG. 5 illustrates the condition of the apparatus of FIG. 4 after the switch 45 had been closed so that the surface tension of the mercury was broken and a portion thereof flowed into the right end of the extension 40C.

It has been found in practice that the voltage applied between the starter electrode and the electrode contained in the mercury is not critical and extends over a range of from a few volts to several hundred volts. Likewise the current required for actuating the switch assembly is not critical with a few milliamperes being adequate. Either alternating or direct current serves to operate the switch. Thus it will be evident to persons skilled in the art that the switch can be manufactured at a very low cost and can be used for a great number of applications, particularly those which today require the use of a relay.

What I claim is:

I. An electrical-to-mechanical converter comprising in combination: a container having first and second portions; in pool of mercury disposed in said first portion of said container with the surface tension of the mercury holding part of the mercury elevated above said second portion of the container and above a path within said container connecting said first and second portions; a conductive fluid inside said container and in engagement with the surface of said mercury; a first electrode engaged with said mercury; a second electrode engaged with said conductive fluid; and means supporting said container for movement from a first position when the mercury is located primarily in said first portion to a second position when part of the mercury flows to said second portion, whereby the passage of current between said electrodes through said fluid and said mercury causes the surface tension of the mercury to be broken.

2. The apparatus of claim I wherein said container has a depressed portion for holding the mercury and an elongated extension portion at an elevation above the lower surface of the depressed portion, the volume of mercury being such that the surface tension thereof holds part of the mercury above the lower surface of said extension portion when said container is in its said first position, and wherein a part of the mercury flows into said extension portion when the surface tension is broken.

3. The apparatus of claim I wherein said fluid is a conductive liquid.

4. The apparatus of claim 3 wherein said liquid is potassium hydroxide.

5. An electrical switch assembly comprising in combination: a container having a first surface and a second surface, a pool of mercury supported by said first surface of said container with a part of the mercury being held above said second surface of the container due to the surface tension of the pool of mercury; a conductive fluid inside said container and engaged with said mercury; first and second electrodes electrically engaged with said fluid and said mercury; means supporting said container for pivotal movement from a first position wherein part of said first surface is below part of said second surface to a second position in response to the flow of mercury onto said second surface; and first electric switch means positioned adjacent said container for actuation in response to the pivotal movement of said container.

6. The apparatus of claim 5 including reset means controlled by said switch means for moving said container from its said second to its said first position.

7. The method of converting an electric signal to a mechanical movement comprising the steps of placing a pool of mercury in a container together with a conductive fluid and position ing the container such that the mercury has a convex portion extending upwardly into the fluid due to the surface tension of the mercury, supporting the container such that a first part of the interior thereof is below the upper part of the convex portion of the mercury with said part being in open communication with the mercury and with the container supported for movement from a first to a second position when the surface tension of the mercury is broken and part of the mercury flows into said first part of the container; and applying an electric signal between the fluid and the mercury to thereby break the surface tension of the mercury. 

1. An electrical-to-mecHanical converter comprising in combination: a container having first and second portions; a pool of mercury disposed in said first portion of said container with the surface tension of the mercury holding part of the mercury elevated above said second portion of the container and above a path within said container connecting said first and second portions; a conductive fluid inside said container and in engagement with the surface of said mercury; a first electrode engaged with said mercury; a second electrode engaged with said conductive fluid; and means supporting said container for movement from a first position when the mercury is located primarily in said first portion to a second position when part of the mercury flows to said second portion, whereby the passage of current between said electrodes through said fluid and said mercury causes the surface tension of the mercury to be broken.
 2. The apparatus of claim 1 wherein said container has a depressed portion for holding the mercury and an elongated extension portion at an elevation above the lower surface of the depressed portion, the volume of mercury being such that the surface tension thereof holds part of the mercury above the lower surface of said extension portion when said container is in its said first position, and wherein a part of the mercury flows into said extension portion when the surface tension is broken.
 3. The apparatus of claim 1 wherein said fluid is a conductive liquid.
 4. The apparatus of claim 3 wherein said liquid is potassium hydroxide.
 5. An electrical switch assembly comprising in combination: a container having a first surface and a second surface, a pool of mercury supported by said first surface of said container with a part of the mercury being held above said second surface of the container due to the surface tension of the pool of mercury; a conductive fluid inside said container and engaged with said mercury; first and second electrodes electrically engaged with said fluid and said mercury; means supporting said container for pivotal movement from a first position wherein part of said first surface is below part of said second surface to a second position in response to the flow of mercury onto said second surface; and first electric switch means positioned adjacent said container for actuation in response to the pivotal movement of said container.
 6. The apparatus of claim 5 including reset means controlled by said switch means for moving said container from its said second to its said first position.
 7. The method of converting an electric signal to a mechanical movement comprising the steps of placing a pool of mercury in a container together with a conductive fluid and positioning the container such that the mercury has a convex portion extending upwardly into the fluid due to the surface tension of the mercury, supporting the container such that a first part of the interior thereof is below the upper part of the convex portion of the mercury with said part being in open communication with the mercury and with the container supported for movement from a first to a second position when the surface tension of the mercury is broken and part of the mercury flows into said first part of the container; and applying an electric signal between the fluid and the mercury to thereby break the surface tension of the mercury. 